3D printers are still _____ expensive for most of us ______ afford.
–What did the policeman say to you just now?--He asked ______ when the accident happened.
-- What did your sister say _____ you?-- She reminded me _____ her birthday.
I’m usually free _____ Tuesday _____ Thursday.
There are _____ places of interest we could visit in Beijing.
-- Did you go to see the doctor yesterday?-- Yes, the doctor advised me ________ too much junk food.